I'm not sure how many people really realize this, but Colors is the first and ONLY application, homebrew or commercial that has EVER used the pressure sensitivity of the DS touchscreen (correct me if I'm wrong, but I've yet to see any - and even if one or two DO use it, they don't use it anywhere near as effectively as Colors does).
Just a quick note: as far as I know, you are correct. Commercial games in fact are incapable of using this pressure sensitivity due to a simple fact. The ARM7 controls the touchscreen, and the ARM7 for commercial games is supplied by Nintendo and cannot be modified by the third-party company. The Nintendo-supplied ARM7 only allows developers to determine whether the touchscreen is being touched or not; it doesn't report any sort of pressure at all, so developers cannot take advantage of it.
I think the prime hunters demo is pressure sensitive, If you lightly touch the option it won't select, But if you just regularly touch it it will select.